1. Field of the Invention
The present invention relates to a method of controlling a focus lens which is movable within a predetermined range so as to focus the focus lens on a subject, and an apparatus for controlling the focus lens by using the method.
2. Description of the Related Art
Recently, digital photographing apparatuses with an auto-focus function have been developed. The autofocus function performs focusing by analyzing image signals while moving a focus lens.
A focus lens is typically movable between the limits of a far position (for focusing on distant objects) and a near position (for focusing on near objects). Conventionally, the auto focus function is performed in several steps. First, the present position of the focus lens is determined, setting a close boundary position between the near and far position. Next, the focus lens is moved from the close boundary position to the far position. While the focus lens moves, the digital photographing apparatus captures and analyzes image signals. The target position for the focus lens is thereby determined.
There are disadvantages to this conventional method and apparatus for performing an auto-focus function. For example, even though a target position of the focus lens is not between the present position of the focus lens and the near position, if the present position of the focus lens is in closer proximity to the near position, then focus lens will be moved from near position to the far position in determining the target position. Although in principle the movement of the focus lens between the near position and the present position is unnecessary, conventionally the focus lens is moved through all possible positions. Unnecessary movement of the focus lens causes problems, such as wasteful power consumption and an increase in scanning time.